Amniotic membrane extract differentially regulates human peripheral blood T cell subsets, monocyte subpopulations and myeloid dendritic cells.

The discovery of the immunoregulatory potential of human amniotic membrane (hAM) propelled several studies focusing on its application for the treatment of immunological disorders. However, there is little information regarding the effects of hAM on distinct activation and differentiation stages of immune cells. Here, we aim to investigate the effect of human amniotic membrane extract (hAME) on the pattern of cytokine production by T cells, monocytes and myeloid dendritic cells (mDCs). For this purpose, peripheral blood mononuclear cells (PBMCs) from eight healthy individuals were stimulated in vitro in the presence or absence of hAME. Mitogen-induced proliferation of PBMCs and cytokine production among the distinct T cell functional compartments, monocyte subpopulations and mDCs were evaluated. hAME displayed an anti-proliferative effect and decreased the frequency of T cells producing tumor necrosis factor (TNF)α, interferon (IFN)γ and interleukin (IL)-2, for all T cell functional compartments. The frequency of IL-17 and IL-9-producing T cells was also reduced. The inhibition of mRNA expression of granzyme B, perforin and NKG2D by CD8+ T cells and γδ T cells and the augment of FoxP3 and IL-10 in CD4+ T cells and IL-10 in regulatory T cells were also observed. Furthermore, hAME inhibited IFNγ-induced protein (IP)-10 expression by classical and non-classical monocytes, without hampering the production of TNFα and IL-6 by monocytes and mDCs. These results suggest that hAME exerts an anti-inflammatory effect on T cells, still at a different extent for distinct T cell functional compartments.

Different frequencies of Tc17/Tc1 and Th17/Th1 cells in chronic spontaneous urticaria.

BACKGROUND: Chronic urticaria is associated with an immune dysregulation usually mediated by T lymphocytes. Recently, Th17 and Tc17 have been implicated in autoimmune diseases; however, their role in urticaria is not clear yet. METHODS: For the study we recruited 20 patients [10 of them had autoreactive chronic spontaneous urticaria (positive autologous intradermal serum test response, ASST+), and the other 10 were nonautoreactive chronic spontaneous urticaria patients (ASST-)] and 17 healthy age- and gender-matched controls (HG). The frequency and functional activity of Th17/Tc17 and Th1/Tc1 cells were evaluated by flow cytometry and type 2 cytokine mRNA by real-time PCR. RESULTS: Our results demonstrated a significant decrease in Th17 frequency in both chronic urticaria groups compared to HG; regarding the amount of IL-17, at the single cell level, it was reduced in ASST- compared to HG. Concerning the Th1 and Th17 cells producing IFN-γ, IL-2, and TNF-α, a lower frequency was noted in chronic urticaria patients compared to HG. In contrast, a significantly increased frequency of Tc1 cells producing these cytokines was noted in ASST+ compared to HG and ASST-. Also, the frequency of Tc17 cells producing TNF-α was increased in ASST+ compared to HG; however, with respect to the amount of TNF-α, at the single cell level, we found a decrease in ASST+ compared to HG. Regarding type 2 cytokine mRNA, a higher expression was verified in ASST+ compared to HG. CONCLUSION: Our data suggest a probable involvement of cytotoxic T cells, mainly the Tc1 and Tc17 subsets, in chronic urticaria, particularly in the ASST+ group.

Distribution and functional plasticity of peripheral blood Th(c)17 and Th(c)1 in rheumatoid arthritis.

UNLABELLED: With the discovery of Th17 cells, it became unclear whether rheumatoid arthritis (RA) is a Th1-mediated and/or a Th17-mediated disease. OBJECTIVE: The aim of this study was to identify and characterize the pro-inflammatory function of IL-17-producing T cell subsets (Th(c)17) in RA. Flow cytometry analysis was performed on peripheral blood from RA patients with inactive or low disease activity (LDA, n = 19) and moderate to high disease activity (HDA, n = 13) to analyze the number and functional activity of Th(c)17 and Th(c)1 cell subsets according to the frequency of IL-2-, TNF-α- and IFN-γ-producers cells, as well as, their cytokine amount. Additionally, 13 age-matched healthy volunteers were added to the study. Our data point to a slight increase in Tc17 frequency in RA patients, more evident in HDA, and a higher ability of Th17 to produce IL-17, whereas a lower production of TNF-α was noted either in Th17 or Tc17 cells, particularly from HDA. A similar decrease was observed in Th(c)1 for almost all studied pro-inflammatory cytokines, with the exception of IL-2, which was increased in Tc1 from LDA patients. Analysing the proportion of pro-inflammatory cytokines-producing cells, a polarization to a Tc1 phenotype seemed to occur in CD8 T cells, while CD4 T cells appear to be decreased in their frequency of IFN-γ-producing cells. Taken together, the functional plasticity features of Th17 and Tc17 cells suggest a particular contribution to the local cytokine production, pointing an underestimated role, namely of Tc1 and Tc17 cells, in the RA pathophysiology.

Changes in natural killer cell subpopulations over a winter training season in elite swimmers.

Immune changes and increased susceptibility to infection are often reported in elite athletes. Infectious episodes can often impair training and performance with consequences for health and sporting success. This study monitored the occurrence of episodes of upper respiratory symptoms (URS) and the variation in circulating NK cells, CD56(bright) and CD56(dim) NK cells subpopulations, over a winter swimming season. Nineteen national elite swimmers and 11 non-athlete controls participated in this study. URS episodes were monitored using daily log books. Blood samples were taken at rest at four time points during the season: before the start of the season (t1--middle September), after 7 weeks of an initial period of gradually increasing training load (t2--early November), after 6 weeks of an intense training cycle (t3--late February) and 48 h after the main competition (t4--early April) and from the controls at three similar time points (t1--early November; t2--late February; t3--early April). In the swimmers, the occurrence of URS clustered around the periods of elevated training load (67 %). No URS were reported at equivalent time points in the non-athletes. Athletes showed a decrease in the percentage (t2 = 21 %; t3 = 27 %; t4 = 17 %) and absolute counts of circulating NK cells (t2 = 35 %; t3 = 22 %; t4 = 22 %), coinciding with the periods of increased training load, never recovering to the initial values observed at the start of the season. The reduction in the CD56(dim) and an increase in the CD56(bright) NK cell subpopulations were significant at t2 and t3 (p < 0.05). Concomitant with the fall in values of NK cells, in athletes that shown more than three URS episodes, a moderate correlation (r = 0.493; p = 0.036) was found between CD56(bright)/CD56(dim) ratio and the number of URS episodes after the more demanding training phase (t3). At t3, a lower value of CD56 cell counts was found in the group who reported three or more URS episodes (t = 2.239; p = 0.032). A progressive significant decrease in the expression of CD119, the receptor for IFN-γ, on the CD56(dim) cells was found over the season and an elevation in Granzyme B expression was coincident with the more demanding training phases. Periods of highly demanding training seem to have a negative impact on innate immunity mediated by NK cell subsets, which could partially explain the higher frequency of URS observed during these training phases.

Functional characterization of peripheral blood dendritic cells and monocytes in systemic lupus erythematosus.

With the purpose of contributing to a better knowledge of the APCs functional activity in SLE, we evaluated the distribution and functional ability to produce pro-inflammatory cytokines (TNF-α, IL-1ß, IL-6 and IL-12) of peripheral blood (PB) monocytes and DC (tDC), particularly myeloid (mDC) and CD14(-/low)CD16(+) DC subpopulations comparing them with those obtained from healthy individuals. The study was performed in 34 SLE patients with diverse disease activity scores (SLEDAI) and 13 healthy age- and sex-matched controls (NC). Our results show an overall decrease in absolute number and relative frequency of tDC in SLE patients with active disease when compared to those with inactive disease and NC, although this decrease did not seem to have an effect on the distribution of PB DC subsets. The monocytes number in SLE patients was similar to those found in NC, whereas a higher frequency of monocytes producing cytokines as well as the amount of each cytokine per cell found without stimulation was particularly observed in those patients with active disease. After stimulation, we observed a higher frequency of IL-12-producing monocytes in active SLE patients. On the other hand, we found among DCs higher frequencies of cytokine-producing CD14(-/low)CD16(+) DCs and a higher amount of cytokines produced per cell, particularly in active disease. These findings support an increased production of inflammatory cytokines by APCs in active SLE, mostly associated with alterations in CD14(-/low)CD16(+) DC subset homeostasis that might contribute to explain the dynamic role of these cells in disease pathogenesis.

Cytokine production by monocytes, neutrophils, and dendritic cells is hampered by long-term intensive training in elite swimmers.

Elite level athletes seem to be prone to illness especially during heavy training phases. The aim of this study was to investigate the influence of long term intensive training on the functional features of innate immune cells from high competitive level swimmers, particularly the production of inflammatory mediators and the possible relationship with upper respiratory symptoms (URS) occurrence. A group of 18 swimmers and 11 healthy non athletes was studied. Peripheral blood samples were collected from athletes after 36 h of resting recovery from exercise at four times during the training season and at three times from non athletes. Samples were incubated in the presence or absence of LPS and IFN-γ and the frequency of cytokine-producing cells and the amount produced per cell were evaluated by flow cytometry. In addition, plasma cortisol levels were measured and URS recorded through daily logs. The athletes, but not the controls, showed a decrease in the number of monocytes, neutrophils, and dendritic cell (DC) subsets and in the amount of IL-1ß, IL-6, IL-12, TNF-α, and MIP-1ß produced after stimulation, over the training season. Differences were most noticeable between the first and second blood collections (initial increase in training volume). Athlete's cortisol plasma levels partially correlated with training intensity and could help explain the reduced in vitro cell response to stimulation. Our results support the idea that long-term intensive training may affect the function of innate immune cells, reducing their capacity to respond to acute challenges, possibly contributing to an elevated risk of infection.

Human Bone Marrow Mesenchymal Stromal/Stem Cells Regulate the Proinflammatory Response of Monocytes and Myeloid Dendritic Cells from Patients with Rheumatoid Arthritis.

Rheumatoid arthritis (RA) is a disabling autoimmune disease whose treatment is ineffective for one-third of patients. Thus, the immunomodulatory potential of mesenchymal stromal/stem cells (MSCs) makes MSC-based therapy a promising approach to RA. This study aimed to explore the immunomodulatory action of human bone marrow (BM)-MSCs on myeloid dendritic cells (mDCs) and monocytes, especially on cytokines/chemokines involved in RA physiopathology. For that, LPS plus IFNγ-stimulated peripheral blood mononuclear cells from RA patients (n = 12) and healthy individuals (n = 6) were co-cultured with allogeneic BM-MSCs. TNF-α, CD83, CCR7 and MIP-1ß protein levels were assessed in mDCs, classical, intermediate, and non-classical monocytes. mRNA expression of other cytokines/chemokines was also evaluated. BM-MSCs effectively reduced TNF-α, CD83, CCR7 and MIP-1ß protein levels in mDCs and all monocyte subsets, in RA patients. The inhibition of TNF-α production was mainly achieved by the reduction of the percentage of cellsproducing this cytokine. BM-MSCs exhibited a remarkable suppressive action over antigen-presenting cells from RA patients, potentially affecting their ability to stimulate the immune adaptive response at different levels, by hampering their migration to the lymph node and the production of proinflammatory cytokines and chemokines. Accordingly, MSC-based therapies can be a valuable approach for RA treatment, especially for non-responder patients.

Frequency and functional activity of Th17, Tc17 and other T-cell subsets in Systemic Lupus Erythematosus.

To compare frequency and functional activity of peripheral blood (PB) Th(c)17, Th(c)1 and Treg cells and the amount of type 2 cytokines mRNA we recruited SLE patients in active (n=15) and inactive disease (n=19) and healthy age- and gender-matched controls (n=15). The study of Th(c)17, Th(c)1 and Treg cells was done by flow cytometry and cytokine mRNA by real-time PCR. Compared to NC, SLE patients present an increased proportion of Th(c)17 cells, but with lower amounts of IL-17 per cell and also a decreased frequency of Treg, but with increased production of TGF-beta and FoxP3 mRNA. Iotan active compared to inactive SLE, there is a marked decreased in frequency of Th(c)1 cells, an increased production of type 2 cytokines mRNA and a distinct functional profile of Th(c)17 cells. Our findings suggest a functional disequilibrium of T-cell subsets in SLE which may contribute to the inflammatory process and disease pathogenesis.

Immunomodulatory effect of human bone marrow-derived mesenchymal stromal/stem cells on peripheral blood T cells from rheumatoid arthritis patients.

Rheumatoid arthritis (RA) is a Th1/Th17-mediated autoimmune disease whose current treatment, consisting in the blockage of inflammatory cytokines by disease-modifying antirheumatic drugs, is not effective for all patients. The therapeutic potential of mesenchymal stromal/stem cells' (MSCs) immunomodulatory properties is being explored in RA. Here, we investigate the effect of human bone marrow (BM)-MSCs on the expression of cytokines involved in RA physiopathology by the distinct functional compartments of CD4+ and CD8+ T cells from RA patients. Peripheral blood mononuclear cells from healthy individuals (n = 6) and RA patients (n = 12) were stimulated with phorbol myristate acetate plus ionomycin and cultured in the presence/absence of BM-MSCs. The expression of (interleukin) IL-2, tumor necrosis factor alpha (TNF-α), and interferon-gamma (IFN-γ) was evaluated in naive, central memory, effector memory, and effector CD4+ and CD8+ T cells, whereas IL-6, IL-9, and IL-17 expression was measured in total CD4+ and CD8+ T cells. mRNA expression of IL-4, IL-10, transforming growth factor beta (TGF-ß), cytotoxic T-lymphocyte-associated antigen 4, and/or forkhead box P3 was quantified in fluorescence-activated cell sorting-purified CD4+ T cells, CD8+ T cells, and CD4+ Treg. BM-MSCs inhibited the production of TNF-α, IL-17, IL-6, IL-2, IFN-γ, and IL-9 by T cells from RA patients, mainly by reducing the percentage of cells producing cytokines. This inhibitory effect was transversal to all T cell subsets analyzed. At mRNA level, BM-MSCs increased expression of IL-10 and TGF-ß by CD4+ and CD8+ T cells. BM-MSCs displayed a striking inhibitory action over T cells from RA patients, reducing the expression of cytokines involved in RA physiopathology. Remarkably, BM-MSC-derived immunomodulation affected either naive, effector, and memory T cells.

Subcutaneous immunotherapy induces alterations in monocytes and dendritic cells homeostasis in allergic rhinitis patients.

BACKGROUND: Specific subcutaneous immunotherapy (SCIT) can achieve long-term remission in patients with allergic rhinitis (AR) through complex and still unknown mechanisms. The aim of this study is to evaluate the effect of SCIT over CD16+ and CD16- monocytes, myeloid (mDCs) and plasmacytoid dendritic cells (pDCs) in patients with AR, comparatively to pharmacological standard treatment (non-SIT). METHODS: The relative frequency and absolute number of monocytes and DC subsets, the frequency of these cells producing TNFα after in vitro stimulation with Dermatophagoides pteronyssinus (Dpt) extract, and the expression levels of receptor-bound IgE or IgG were assessed by flow cytometry, in peripheral blood samples from 23 healthy individuals (HG) and 43 participants with AR mono-sensitized to Dpt; 10 with non-SIT treatment and 33 under SCIT, just before (SCIT-T0) and 4 h after administration (SCIT-T4). Moreover, IFNα mRNA expression was evaluated in purified pDCs, by qRT-PCR. RESULTS: After SCIT administration we observed a strong decrease of circulating pDCs, although accompanied by higher levels of IFNα mRNA expression, and an increase of circulating CD16+ monocytes. AR participants under SCIT exhibited a higher expression of receptor-bound IgE in all cell populations that expressed the high affinity receptor for IgE (FcεRI) and a higher frequency of CD16+ monocytes producing TNFα. Conversely, we observed a decrease in the frequency of mDCs producing TNFα in AR under SCIT, similar to the observed in the control group. CONCLUSIONS: SCIT seems to induce numeric, phenotypic, and functional changes in circulating monocytes and dendritic cells, contributing at least in part to the well described immunological alterations induced by this type of immunotherapy.

Effect of human bone marrow mesenchymal stromal cells on cytokine production by peripheral blood naive, memory, and effector T cells.

INTRODUCTION: The different distribution of T cells among activation/differentiation stages in immune disorders may condition the outcome of mesenchymal stromal cell (MSC)-based therapies. Indeed, the effect of MSCs in the different functional compartments of T cells is not completely elucidated. METHODS: We investigated the effect of human bone marrow MSCs on naturally occurring peripheral blood functional compartments of CD4(+) and CD8(+) T cells: naive, central memory, effector memory, and effector compartments. For that, mononuclear cells (MNCs) stimulated with phorbol myristate acetate (PMA) plus ionomycin were cultured in the absence/presence of MSCs. The percentage of cells expressing tumor necrosis factor-alpha (TNF-α), interferon gamma (IFNγ), and interleukin-2 (IL-2), IL-17, IL-9, and IL-6 and the amount of cytokine produced were assessed by flow cytometry. mRNA levels of IL-4, IL-10, transforming growth factor-beta (TGF-ß), and cytotoxic T-lymphocyte-associated protein 4 (CTLA4) in purified CD4(+) and CD8(+) T cells, and phenotypic and mRNA expression changes induced by PMA + ionomycin stimulation in MSCs, were also evaluated. RESULTS: MSCs induced the reduction of the percentage of CD4(+) and CD8(+) T cells producing TNF-α, IFNγ, and IL-2 in all functional compartments, except for naive IFNγ(+)CD4(+) T cells. This inhibitory effect differentially affected CD4(+) and CD8(+) T cells as well as the T-cell functional compartments; remarkably, different cytokines showed distinct patterns of inhibition regarding both the percentage of producing cells and the amount of cytokine produced. Likewise, the percentages of IL-17(+), IL-17(+)TNF-α(+), and IL-9(+) within CD4(+) and CD8(+) T cells and of IL-6(+)CD4(+) T cells were decreased in MNC-MSC co-cultures. MSCs decreased IL-10 and increased IL-4 mRNA expression in stimulated CD4(+) and CD8(+) T cells, whereas TGF-ß was reduced in CD8(+) and augmented in CD4(+) T cells, with no changes for CTLA4. Finally, PMA + ionomycin stimulation did not induce significant alterations on MSCs phenotype but did increase indoleamine-2,3-dioxygenase (IDO), inducible costimulatory ligand (ICOSL), IL-1ß, IL-8, and TNF-α mRNA expression. CONCLUSIONS: Overall, our study showed that MSCs differentially regulate the functional compartments of CD4(+) and CD8(+) T cells, which may differentially impact their therapeutic effect in immune disorders. Furthermore, the influence of MSCs on IL-9 expression can open new possibilities for MSC-based therapy in allergic diseases.

Human Bone Marrow-Derived Mesenchymal Stromal Cells Differentially Inhibit Cytokine Production by Peripheral Blood Monocytes Subpopulations and Myeloid Dendritic Cells.

The immunosuppressive properties of mesenchymal stromal/stem cells (MSC) rendered them an attractive therapeutic approach for immune disorders and an increasing body of evidence demonstrated their clinical value. However, the influence of MSC on the function of specific immune cell populations, namely, monocyte subpopulations, is not well elucidated. Here, we investigated the influence of human bone marrow MSC on the cytokine and chemokine expression by peripheral blood classical, intermediate and nonclassical monocytes, and myeloid dendritic cells (mDC), stimulated with lipopolysaccharide plus interferon (IFN)γ. We found that MSC effectively inhibit tumor necrosis factor- (TNF-) α and macrophage inflammatory protein- (MIP-) 1ß protein expression in monocytes and mDC, without suppressing CCR7 and CD83 protein expression. Interestingly, mDC exhibited the highest degree of inhibition, for both TNF-α and MIP-1ß, whereas the reduction of TNF-α expression was less marked for nonclassical monocytes. Similarly, MSC decreased mRNA levels of interleukin- (IL-) 1ß and IL-6 in classical monocytes, CCL3, CCL5, CXCL9, and CXCL10 in classical and nonclassical monocytes, and IL-1ß and CXCL10 in mDC. MSC do not impair the expression of maturation markers in monocytes and mDC under our experimental conditions; nevertheless, they hamper the proinflammatory function of monocytes and mDC, which may impede the development of inflammatory immune responses.

Sera from patients with active systemic lupus erythematosus patients enhance the toll-like receptor 4 response in monocyte subsets.

BACKGROUND: Systemic Lupus Erythematosus (SLE) is an auto-immune disease whose complex pathogenesis remains unraveled. Here we aim to explore the inflammatory ability of SLE patients' sera upon peripheral blood (PB) monocyte subsets and myeloid dendritic cells (mDCs) obtained from healthy donors. METHODS: In this study we included 11 SLE patients with active disease (ASLE), 11 with inactive disease (ISLE) and 10 healthy controls (HC). PB from healthy donors was stimulated with patients' sera, toll-like receptor (TLR) 4 ligand - lipopolysaccharide or both. The intracellular production of TNF-α was evaluated in classical, non-classical monocytes and mDCs, using flow cytometry. TNF-α mRNA expression was assessed in all these purified cells, after sera treatment. RESULTS: We found that sera of SLE patients did not change spontaneous TNF-α production by monocytes or dendritic cells. However, upon stimulation of TLR4, the presence of sera from ASLE patients, but not ISLE, significantly increased the intracellular expression of TNF-α in classical and non-classical monocytes. This ability was related to titers anti-double stranded DNA antibodies in the serum. High levels of anti-TNF-α in the patients' sera were associated with increased TNF-α expression by co-cultured mDCs. No relationship was found with the levels of a wide variety of other pro-inflammatory cytokines. A slight increase of TNF-α mRNA expression was observed in these purified cells when they were cultured only in the presence of SLE serum. CONCLUSIONS: Our data suggest that SLE sera induce an abnormal in vitro TLR4 response in classical and non-classical monocytes, reflected by a higher TNF-α intracellular expression. These effects may be operative in the pathogenesis of SLE.

Haematological changes in elite kayakers during a training season.

This study monitored haematological markers in response to training load in elite kayakers during a training season. The sample comprised eight elite kayakers aged 22 ± 4.2 years with a 77.2 ± 6.7 kg body mass and a 177.5 ± 5.6 cm stature. The initial [Formula: see text]O(2max) was 61.2 ± 5.5 mL·kg(-1)·min(-1). The control group consisted of six healthy males, aged 18.6 ± 1.1 years, with an 81.3 ± 13.8 kg body mass and a 171.9 ± 4.5 cm stature. Blood samples were collected at the beginning of the training season after an off-training period of six weeks (t(0)), at the 11th week after the application of high training volumes (t(1)), at the 26th week after an intense training cycle (t(2)), and at the 31st week at the end of a tapering phase (t(3)). Differences between time points were detected using ANOVA and the Bonferroni post hoc test. Significant changes were found after the intense training cycle (t(2)), lymphocytes decreased while haemoglobin, mean corpuscular volume, mean corposcular haemoglobin, mean concentration of corpuscular hemoglobin concentration, platelets distribution width, and red blood cell distribution width values increased when compared with baseline values. At t(3), a reduction in monocyte numbers and an increase in mean platelet volume compared with baseline values were seen. By reducing the volume and intensity of training, many variables returned to values close to those at baseline. Although many athletes had accumulated responses over time due to training, they still suffered transient changes that appear to be influenced by training load. Haemorheology monitoring may help detect health risks, especially during times of intensified training.

Diferenças em populações de células exterminadoras naturais (Natural Killers-NK) sanguíneas periféricas entre atletas de caiaque e não atletas / Differences in peripheral blood Natural Killer cell populations between elite kayakers and non-athletes

INTRODUÇÃO: O exercício estressante prolongado tem sido associado a uma depressão transitória da função imune, com rotinas de treinamento e competição intensas e prolongadas capazes de levar os atletas a uma deficiência imune. OBJETIVO: O objetivo deste estudo foi observar se o treinamento cr ônico foi capaz de produzir diferenças sustentáveis no sangue periférico (SP) subpopulações de leucócitos (LEU, granulócitos, monócitos, linfócitos totais, linfócitos B e T, e células CD4+ e CD8+T e células natural killers) de atletas de caiaque de elite quando comparados com não atletas. MÉTODOS: A amostra incluiu 13 homens atletas de caiaque de elite, 20 ± 3 anos, 75,0kg ± 7,9 peso e 177,3 ± 7,1 cm estatura. O VO2max foi 58,3 ± 7,8mL.kg.min-1. O grupo de não atletas incluiu sete homens saudáveis, idade 18 ± 1 ano de idade, 81,3 ± 13,8Kg de peso corporal e 171,9 ± 4,5cm de estatura. As amostras de sangue dos atletas foram coletadas no início da temporada de treinamento, após um período fora do treinamento de seis semanas. Populações de células sanguíneas periféricas foram identificadas por análise de citometria de fluxo. Para identificar as diferenças entre os grupos de atletas e não atletas, o teste U de Mann-Whitney foi utilizado. RESULTADOS: N ão foram identificadas diferenças entre os atletas de caiaque treinados e não atletas em repouso, exceto para células natural killers (CD3-CD56+) e os valores da subpopulação CD3-CD56+CD8+ os quais foram mais baixos nos atletas. CONCLUSÃO: Nosso estudo encontrou que, após um período prolongado sem treinamento (seis semanas), somente a população de NK CD3-CD56+ e, em especial, a subpopulação de altamente citotóxica CD3-CD56+CD8+ apresentou níveis mais baixos nos atletas de elite quando comparados com os homens destreinados.

INTRODUCTION: Prolonged strenuous exercise has been associated with a transient depression of immune function, with prolonged intense training schedules and competition able to lead to immune impairment in athletes. OBJETIVE: The objective of this study was to see if chronic training was able to produce sustained differences in the peripheral blood (PB) leukocyte subpopulations (WBC, granulocytes, monocytes, total lymphocytes, B and T lymphocytes, CD4+ and CD8+ T cells and Natural Killer cells) of elite kayakers when compared to non-athletes. METHODS: The sample comprised 13 elite male kayakers, 20 ± 3 years old, 75.0 kg ±7.9 weight and 177.3±7.1 cm stature. The VO2max was 58.3±7.8 mL.kg.min-1. The Non-athlete group comprised 7 health males, aged 18±1 years old, 81.3±13.8 kg of weight and 171.9±4.5cm stature. The athlete's blood samples were collected at the beginning of the training season, after an off period of six weeks of training. Peripheral blood cell populations were identified by flow cytometry analysis. To verify the differences between the athlete and non-athlete groups the Mann-Whitney U Test was used. RESULTS: No differences between the trained kayakers and the non-athletes were found at rest except for Natural Killer cells (CD3-CD56+) and the CD3-CD56+CD8+ subset values that were lower in the athletes. CONCLUSION: Our study found that after a prolonged time without training (six weeks) only the NK CD3-CD56+ population and particularly the highly cytotoxic CD3-CD56+CD8+ subpopulation had lower levels in the elite athletes when compared to the untrained men.